Desulfurization of hydrocarbons



J 3,166,492 f r 'DESULFURIZATION 6F HYDROCARBONS Georg Richard Schultze,Friedrich Boberg, and Gerhard Menzel, Hannover, Germany, assignors toDeu'tsche Goldand Silher-Scheideaustalt' .vormals Roessler, Frankfurt amMain, Germany N Drawing. Filed Dec. 13, 1960, Ser. No. 556,919 1 Claim.(Cl. 208237) The present invention relates to an improved process forthe desulfurization ofhydrocarbons.

It is known that sulfur compounds on treatment with metallic sodium orsodium alloys undergo changes and can even lose their sulfur. especiallyactive and has been proposed as preferred for the desulfurization ofpetroleum products.

In the desulfurization of hydrocarbons, it is of particular advantageiftthe process only effects removal of the sulfur anddoes not efiectremoval of the hydrocarbon residues of the sulfur compounds originallypresent. This would, for example, signify that, when sodium is used, thesulfur present in the hydrocarbons should after completion of thetreatment be converted to sodium sulfide while the hydrocarbon radicalsoriginally bonded to the sulfur should be altered in such a way thatthey remain with desulfurized hydrocarbon. However, with the exceptionof hydrogenation processes, most of the desulfurizing processes usedtoday in mineral oil technology remove the sulfur compounds. as a whole,that is, the organic components bound to the sulfur are removed alongwith the sulfur.

The sulfur compounds occurring in mineral oils exhibit differentactivities with sodium. Mercaptans react easily with sodium with theformation of mercaptides. The sodium mercaptides formed are difficultlysoluble in hydrocarbons, so that the precipitating reaction products canbe filtered off or centrifugedoff. According to German Patent 956,439this procedure, however, does not lead to a complete desulfurization andas a consequence a sulfuric acid treatment is used after the sodiumtreatment. The sulfur remaining in the treated mineral oil product isderived from the small quantities of dissolved mercaptides. The removalof the dissolved mercaptide by washing with water is not possible as ahydrolysis equilibrium occurs with formation of sodium hydroxide andreformation of the mercaptans. Further reaction of sodium with sodiummercaptide or the thermal treatment of the mercaptide does not elfectconversion of the sulfur into sodium sulfide.

As tests have shown, mixtures of hydrocarbons and sodium mercaptidesremain unchanged even after heating for 10 hours at 260 C. in contactwith an excess of sodium.

According to the invention it was unexpectedly found that the formationof sodium sulfide from sodium mercaptides can easily be effected in thepresence of organic sodium compounds, that is, sodium compoundscontaining a direct sodium to carbon bond. The organic sodium compoundscan be added to the reaction mixture of the hydrocarbons beingdesulfurized or they may be formed therein in situ. Most simply theorganic sodium compounds can be produced in the reaction mixture byreacting organic halogen compounds with sodium. Aliphatic,cycloaliphatic, aromatic or mixed aromaticaliphatic halogen compoundscan be employed for this purpose.

Finely dispersed sodium is thiophe'ne, aliphatic disulfides, aliphaticpolysulfides and aliphatic sulfides do not or do not completely yieldtheir white oil).

3,166,492 Patented Jan. 19, 1965 ice sulfur with formation of sodiumsulfide upon treatment with sodium at temperatures up to 250 C. Incontrast thereto, in the presence of organic sodium compounds,

the sulfurin such compounds in each instance was converted completely tothe desired sodium sulfide.

The sodium sulfide produced in the process accordingto the invention canbe removed by. filtration, centrifuging,

for the desulfurization of crude oils, mineral oil products, coke ovenproducts, synthetic hydrocarbons and the like.

It can be used in combination with other desulfurization procedures toremove the last traces of sulfur.

The treatment with the organic sodium compounds can be effected attemperatures between 20 C. and 200 0, preferably betwen 20 C. and C. Thequantity of organic sodium compound employed should be sufiicient toprovide 2.1 gram atoms of sodium per gram atom of sulfur. In thisoperation it is possible to add part of the sodium required-in the formof sodium dispersion.

The following examples will serve to illustrate several embodiments ofthe process according to the invention. The reactions described in suchexamples were carried out in a four necked flask provided with astirrer, thermometer, dropping funnel (with pressure equalizer connected'to the reaction flask) and a reflux condenser (closed with a dryingtube).

EXAMPLE 1 Desulfurization with the aid. of organic halogen compounds (a)Desulfurization of solutions of mercaptans in hydr0carb0ns.A sufficientquantity of arsodium dispersion in the hydrocarbon was added to 250 cc.of a solution of the mercaptan in the hydrocarbon at room tem peraturewhile stirring so that the sulfur content (1.07%) was converted to thesodium mercaptide. Then a sufficient quantity of the organic halogencompound was added to the mixture while stirring so that the molar ratioof sulfur compound to organic halogen compound was 1:1. The reactionmixture was then heated to 50-60" C. and a sufiicient quantity offurther sodium dispersion added until the molar ratio of organic halogencompound to sodium was 112.2; The mixture was then heated with stirringto 120 C. and such temperature maintained for a further 30 minutes. Thereaction caused typical discolorations to deep blue black. After thereaction mixture had cooled down, methanol was added to decompose theunreacted sodium and the mixture washed with water. The discolorationsdisappeared during such washing. After such washing the hydrocarbonlayer was sulfur free. The sulfur was in the aqueous phase as sodiumsulfide and could be determined iodometrically.

The above desulfurization was carried out on heavy petrol (RP. ISO- C.)and on white oil (B.P. 250- 350 0.), solutions of heptane thiol and ofhexane thiol.

The following compounds were used as the organic halogen compounds:phenyl chloride, phenyl bromide, benzyl chloride, butyl chloride, butylbromide and cyclohexyl bromide.

(b) Desulfnrization of solutions of n-butyl sulfide, nheptyl disulfide,amyl polysulfide and dimezhylthiophene.Phenyl bromide was first added atroom temperature with stirring to 250 cc. of solutions of the sulfurcompounds indicated in hydrocarbons (heavy petrol, The sulfur content ofsuch solutions was 1.07%. Thereafter a sodium dispersion was added. Theratio of sulfur compoundzphenyl bromidezsodium was with sodium alone(that is, without addition of an organic halogen compound) onlyv aportion of the sulfur was converted into sodium sulfide even when usingreaction periods up to 10 hours. only 20% was converted into sodiumsulfide and in the case of the sulfur compounds concerned under (b) only60% was converted in the best instances, namely, the

V polysulfides.

Solutions of tetraphenylthiophene and dibenzothiophene remainedcompletely unaltered upon treatment with sodium alone. Upon addition ofphenyl bromide as under (b) or butyl bromide, complete desulfurizationwas achieved.

(d) Different quantities of the following sulfur compounds weredissolved in 250 cc. of mineral spirits, B.P. 100-180" C., to providesolutions having a total sulfur content of 2.7% in each each case:hexane thiol, tetrahydrothiopyrane, benzyl mercaptan, heptyl disulfide,phenyl ethyl sulfide, thionaphthene and thiophenol.

These solutions were reacted according to (b). The ratio of sulfurcompound: phenyl bromidezsodium was so selected that 1 mol of phenylbromide and 3 gram atoms of sodium were provided for every gram atom ofsulfur present. A 100% desulfurization was attained. When the halogencompound was added the desulfurization was demonstrably not complete.

EXAMPLE 2 Desulfurization using an organic sodium compound (a)Desulfurization with phenyl s0dium.A 0.1 molar suspension of sodiumheptyl mercaptide in xylene was added with stirring to 250 cc. of a 0.1molar solution of phenyl sodium in xylene. The mixture was heated to 120C. and after minutes assumed a deep brown coloration. The mixture wasstirred for a further'30 minutes at 120 C. and after cooling was washedwith water as in Example 1(a). The hydrocarbon phase Was completely freeof sulfur,

In the case of the mercaptans' was added. The mixture was heated whilestirring to 120 C. and such temperature maintained for a further 30minutes. The contents of the flocks assumed a brownish black coloration.Upon washing with water the organic phase became free of sulfur.

EXAMPLE 3 Desulfurizalion of a technical diesel fuel The diesel fuelemployed contained 1.03% of sulfur, had a boiling range of ISO-358 C.and a density of (=0.829.

250 cc. of the diesel fuel were stirred together with 2.84 g. of sodiumdispersed in the same fuel for 30 min; utes at C. After usual processingthe. sulfur content had decreased to 0.79%. Even when longer heatingperiods were employed the sulfur content did not decrease further. Onthe other hand, when 4 g. of phenyl bromide were added, the diesel fuelwas sulfur free after the 30 minutes treatment of 120 C.

We claim:

A process for desulfurizing hydrocarbons contaminated with sulfur whichcomprises reacting at a temperature between 20 and 200 C. metallicsodium with a hydrocarbon halide in contact with said hydrocarboncontaminated with sulfur to form an organic sodium compound in which thesodium is directly bonded to carbon in situ in said hydrocarbon, thequantity of sodium supplied to said hydrocarbon contaminated with sulfurby said organic sodium compound and any residual metallic sodium beingat least 2.1 gram atoms of sodium per gram atom of sulfur contained insaid contaminated hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS

